The invention relates to edible fat-containing products comprising indigestible polyol fatty acid polyesters. In particular, although not exclusively, the invention relates to such products of the emulsion type, such as margarines and low-fat spreads. The invention further relates to processes for the preparation of such products.
Polyol fatty acid polyesters, and in particular, the sugar fatty acid polyesters, such as, e.g., the sucrose fatty acid polyesters, are known as suitable low-calorie fat replacers in edible products. Substantially indigestible for human beings they have physical and organoleptic properties very similar to triglyceride oils and fats conventionally used in edible products. Polyol fatty acid polyesters are also reported to have use as pharmaceutical acceptable agents, e.g., in view of their ability to take up fat soluble substances, such as in particular cholesterol, in the gastrointestinal tract,and subsequently remove those substances from the human body. Accordingly, it is attractive to replace at least part of the fat in edible fat-containing products by polyol fatty acid polyesters.
It is further reported that in food products, the use of polyol fatty acid polyesters which are liquid at body temperature, may give rise to the so-called problem of anal leakage. Accordingly, it is particularly attractive to replace the more solid part (hardstock) of a fat source with polyol fatty acid polyesters.
Edible fat-containing products comprising indigestible polyol fatty acid polyesters are know in the art and described in U.S. Pat. Nos. 3,600,186, 4,005,195, 4,005,196, 4,034,083 and EP Patent Publication Nos. 233 856, 236 288 and 235 836.
In this specification, unless otherwise indicated, the term "fat" refers to edible fatty substances in a general sense, including natural or synthesized fats and oils consisting essentially of triglycerides, such as, for example, soybean oil, sunflower oil, palm oil, coconut oil, margarine oil, fish oil, lard and tallow, which may have been partially or completely hydrogenated or modified otherwise, as well as non-toxic fatty materials having properties similar to triglycerides, which materials may be indigestible, such as for example, waxes, jojoba oil and hydrogenated jojoba oil and polyol fatty acid polyesters referred to hereinafter in more detail. The terms fat and oil are used interchangeably.
In this specification, the term "polyol" is intended to refer to any aliphatic or aromatic compound which comprises at least four free hydroxyl groups. Such polyols in particular include the group of sugar polyols, which comprises the sugars, i.e., the mono-, di- and polysaccharides, the corresponding sugar alcohols and the derivatives thereof having at least four free hydroxyl groups. Examples of sugar polyols include glucose, mannose, galactose, xylose, fructose, sorbose, tagatose, ribulose, xylulose, maltose, lactose, cellobiose, raffinose, sucrose, erythritol, mannitol, lactitol, sorbitol, xylitol and alpha-methylglucoside. A generally used sugar polyol is sucrose.
In this specification, the term "polyol fatty acid polyester" is intended to refer to any such polyesters or mixtures thereof of which, on an average, more than 70% of the polyol hydroxy groups have been esterified with fatty acids.
In this specification by "indigestible" is meant that at least about 70% by weight of the material concerned is not digested by the human body. In this specification, the hydrophile-lipophile balance (HLB) of an emulsifier is used to classify the emulsifier in terms of its relative simultaneous attraction to the oil phase and the water phase of an emulsion; see, for example, Schick, Nonionic Surfactants: Physical Chemistry, pp. 439-47 (Marcel Dekker, Inc., New York, N.Y.; 1987). As noted in Schick at page 439, "[s ]urfactants with a low HLB number normally form W/O emulsions, whereas those with high HLB numbers for O/W emulsion." For purposes of this invention, a low HLB surfactant has an HLB less than about 4.5 and a high HLB surfactant has an HLB greater than about 4.5.
In this specification, by "hardstock" is meant that part of the fat composition is characterized by a slip melting point of above 36.degree. C. "Slip melting point" is defined as the temperature at which the amount of solid phase in the melting fat has become so low that an air bubble is forced upwards in an open capillary filled with the fat.
Fat-containing products and in particular, emulsion type products such as margarines and low-fat spreads, have to comply with requirements such as oral response, thermal stability, cycle stability, spreadability, melting behavior and the like. Often they have to comply with such requirements simultaneously.
In particular, for margarines and low-fat spreads which contain relatively large amounts of polyunsaturated components or require increased softness at lower (refrigerator) temperatures, it can be difficult to simultaneously comply with the requirements for cycle stability, thermal stability and acceptable taste properties.
Stability against temperature changes (cycle stability) is important in view of temperature changes during transport and storage as well as temperature changes which may frequently occur during household use. Improved storage temperature cycle stability is therefore advantageous, if not essential,
Heat stability, i.e., stability in terms of the absence of phase separation and of oil exudation, determines the ambient temperatures at which the product can be used. It will be clear that heat stability requirements are dependent of the climatic zone involved.
In general, the heat stability is governed by the amount of hardstock, i.e., the amount of higher melting fats. A better heat stability, however, in general will result in a deterioration of the oral response, especially after temperature cycling. This is because the oral response largely depends on the melting behavior of the fat phase.
Although not wishing to be bound by an theory, it is believed that the difficult compatability of heat stability, good oral response and cycling stability stems from the fact that good heat stability (e.g., heat stability at 30.degree. C. for 24 hours) generally requires blended fat compositions containing relatively high amounts of higher melting fat fractions such as in particular fat fractions having melting points above mouth temperature. These higher melting fat fractions are believed to be responsible for the adverse effects on oral response and cycling stability.
Generally, in conventional fat-containing products, the higher melting fat fractions crystallize in mixed crystals of non-equilibrium composition, which incorporate considerable amounts of the lower-melting fat fractions. In a well formulated blend, the melting point of the mixed crystals is just below mouth temperature. Accordingly, in the mouth such blends will melt entirely, not giving rise to waxiness and, in the case of emulsions, fully releasing the salt and flavor compounds present in the water phase.
However, when conventional fat-containing products are subjected to temperature cycling, the mixed crystals demix, and a separate, purer fraction of the higher melting fats crystallizes. In this process, a network of crystals is formed, which, if a dispersed water phase is present, surrounds and stabilizes the dispersed water droplets in the form of shells. In the mouth the non or only partially melting network of crystals introduces a waxy taste, and prevents release of salt or flavor compounds from the dispersed water droplets which remain stabilized.
Conventional products displaying good heat stability often combine this property with a rather bad cycling stability and oral response. Conventional products having improved cycle stability due to the presence of a relatively small amount of high melting fats often suffer poor heat stability.
Many of the problems associated with the requirements for cycle stability, thermal stability and acceptable taste properties can be overcome by the compositions and method of the present invention wherein two fat phases in separate emulsions can be combined to tailor the fat properties required for solution of these problems. Also, the problem of anal leakage associated with the use of polyol fatty acid polyesters can be effectively overcome by the method and products of the present invention.